The product thereof



Patented Dec. 25, 1934 UNITED STATES METHOD OF MAKING AN ADHESIVE AND THE PRODUCT THEREOF Glenn Davidson, Charles N. Cone, Irving F. Laucks, and Harry P. Banks, Seattle, Wash,

assignors to I. F. Laucks, hingt corporation of Was c., Seattle, Wash, a on No Drawing. Continuation of application Serial No. 93.534, March 9, 1926. This application July 18, 1931, Serial No. 551,786

24 Claims. (01. 134-233) Our invention relates to the method of making an adhesive and to the product thereof. More particularly, our invention will be described in connection with the problems arising in the art of making veneer panels, but it is to be understood that it is not to be restricted to any such specific application, but is co-extensive in all fields where like problems and conditions obtain.

In general, it may be stated that at the present time there are two processes of making veneer panels.

First-The pieces or plies of wood are dried down to a low moisture content, varying from one to five percent. They are then passed through an adhesive spreader, i. e., rolls, which coat either one or both sides of the pieces or plies of wood, as may be required. The various plies are then assembled in a pile or rack in the proper order, de-. pending on the character of the veneer panel being manufactured,it being understood that these may be either panels composed of an odd number of plies, three, five, seven, etc., in which case the outer faces of the panels of course receive no glue, and in this case panels and fibres of the adjacent plies are disposed at right angles to each other; or they may be veneer panels composed of several plies, the plies being parallel in the adjacent plies, such as in the case of so-called door stiles and rails, or they may be glued on the edges, or in other ways. It should be understood that by plies we do not mean necessarily very thin pieces, as in veneer manufacture, because, in the case of door stiles and rails, the center ply is of some considerable thickness. When the rack or pile of veneer panels thus assembled has been built up to the proper number of pieces contained therein, it is then transferred to a press and a suitable pressure is applied. This pressure varies ordinarily from fifty to two hundred pounds per square inch,.although pressures outside of this range may be employed for certain particular objects. After the pressure is applied, the pressed rack or pile is then held tightly by clamps,'and set aside for a period of time for the setting of the glue to take place. This period ordinarily must be from five to ten hours, depending upon conditions in the plant, but it may of course be as short a time as the glue requires to obtain its set, and it may be as long a time as may be desired after this. It is however, necessary to keep this pressure on the racks until the glue has received its set. After this, the racks are disassembled and the pieces may then be sawed to dimension, and the surfaces planed or sanded 01 finished n a y pecially is worked by the present described .method. Wet cottonwood, containing up to, two hundred per cent moisture (as referred to the dry weight of the wood), is passed through gluespreaders and the glue applied to the surface. The veneer panels thus formed are then placed in a press, the plates of which are heated, and pressure is applied to take out a certain amount of moisture, and to give the glue an initial set or strength sufiicient to hold the plies in the subse' quent operations. After this first step, the veneer panels are passed through a dryer, which reduces the moisture still further. After this, a final pressing is applied in another hot press, during which the moisture in the veneer panel is reduced to a figure which will meet the needs of the particular market into which it is going. In this process, there is a tendency toward dilution of the glue or adhesive by the water in the wood, unless some thickened or jelly form of glue be used, and washing out or squeezing out would take place with a glue in the ordinary syrupy condition. Herein, glue and adhesive are used synonymously.

In connection with the first above-named proces of making a veneer panel of wood plies, heretofore, casein, starch and animal glue have been the types of adhesives used. Blood albumen glue is not used in connection with the first process, because this type of adhesive must ordinarily be subjected to the action of heat. An important objection to the present casein, starch and animal glues is that they are relatively expensive, and the two latter are not water-resistant.

In the second process of. making a veneer panel of wood plies, neither casein, starch or animal glue have been found satisfactory, since either they do not form a jelly or are not water-resistant,- blood albumen having been heretofore used, and being the only type of adhesive that could be used in this process until the present improved method. Blood albumen has a number of disadvantages. It is very difiicult to handle; its source is manifestly limited, and it is therefore relatively expensive; and from the manufacturing of veneer panels point of view, it is particularly objectionable in view of the fact that it stains the wood,--it being remembered that in the case of veneer, the plies may be very thin, so that any action which tends to discolor the wood quickly makes itself apparent.

A primary object of our invention is to provide a veneer panel which overcomes all these and other objections, and to provide such a panel, the plies of wood of which are bound together by a vegetable protein-containing adhesive, particularly a ground oil-seed residue or oil-seed flour.

Heretofore, it has been thought impossible to make an oil-seed residue glue that would be suitable in the manufacture of veneer by the second method. When certain woods are dried below the fibre saturation point, as occurs in the first process above indicated, checking, distortion and splitting occur to a very considerable degree, when the veneer is dried. If, however, the wood is not dried below the fibre saturation point before gluing, but the glue is applied while the moisture is still above the fibre saturation point, then the strains set up in the wood on drying are neutralized by the fibres disposed at right angles to each other, and when the veneer panel is afterwards dried down, no loss results from checking, cracking or distortion. However, adhesives as heretofore made of oil-seed residues become so dilutedby the liquid in-the cellular structure of the wood and are thereby weakened, that the adhesive does not remain on the glue line when pressure is applied to the rack of assembled panels. A primary object of our invention is to overcome this diificulty.

We have foimd that if certain vegetable protein-containing materials in the form of oil-seed residues are properlytreated, an adhesive may be made therefrom in the form of a jelly or a-gel, and when this adhesive in the form of a jelly is spread upon the plies and subjected to pressure, such jelly does not run into the damp wood, but is retained on the glue line and will give such adhesion as to hold the plies together, so that they can be afterwards dried down to the proper percentage of moisture without checking, distortion or splitting. After drying, of course the adhesion is greatly improved. Manifestly, this adhesive in the form of a jelly may also be used in connection with the first process above set forth,namely, upon dry veneer panels.

The strains set up inthe plies of the wood in drying are great, and therefore, the adhesive to achieve the results above indicated, namely, the overcoming of the checking, distortion and splitting incident to drying, must be of great strength. A primary object of our invention is to provide an adhesive satisfying this requirement.

We have found that a number of oil-seed residues can be so treated to form jellies and that when dried these jellies have the property of resisting water penetration so as to form a waterresistant glue, or as sometimes called, a waterproof glue. We have worked with protein-containing substances after the oil has been expressed from a number of oil-seeds, such as peanuts, cottonseed, linseed, soya beans, etc. We have also used casein in this same way. We find that soya beans, after the oil has been expressed, are especially useful for this purpose. In general,

the protein-containing substances, that is the o.l-'

seed residues, must be dispersed or put into colloidal solution. We accomplish the dispersion by the use of alkaline reagents and also by mechanical agitation.

The materials used to form the jelly may either be added before the oil-seed residue materials are dispersed or afterwards. The oil-seed residue material is, of course, stirred into a sufficient quantity of water before either the dispersing agent or the jellying agent is added.

Because of the rigid requirements of veneer manufacture, and particularly are these requirements rigid where the plies of wood have a moisture content equal to that of cell saturation 'or more, not only must the adhesive have the form of a jelly, but it must be of a particular character that will enable it to maintain its jelly form. We have found that if we only use a dispersing agent, as for example, caustic soda and a jellying agent, as for example, formaldehyde, that, although we get a jelly, this jelly still has some tendency to break down on the application of pressure upon the plies of wood and tends to run into the wood. To prevent this break-down of the jelly, we find that certain colloidal precipitates or adsorbent materials, or both together, are useful. For example, we find that by the addition of a certain amount of potassium permanganate we form a jelly which does not break-down, but which remains on the glue line and gives a good adhesion even with damp veneer. It appears that one of the manganese hydrates is precipitated and we believe that this precipitate is responsible for much of the improvement in the jelly. We find also that such precipitate is more efiicient when it is precipitated in the glue rather than if added as a solid. It is possible also that permanganate has some oxidizing effect on the components of the oil-seed residues which may also be beneficial in this respect, as we have found in other glues produced from the same materials in general that oxidizing agents make an improvement.

We have also used adsorbent materials such as wood flour or what is known as sander dust", and find that these have the same effect in stabilizing the jelly.

We call these materials stabilizing agents and under such we would include as equivalents metallic compounds which precipitate colloidal precipitates of the nature of manganese, iron, and aluminum hydrates and others of this nature, such as, for instance, potassium permanganate, ferrous sulphate, aluminum sulphate, as well as adsorbent materials similar to wood. flour, charcoal, as well as inorganic adsorbent materials, such as chalk, calcium carbonate, calcium phosphate. We believe that such precipitates and materials act to form a sort of skeleton, as it were, and thereby stabilize the jelly.

In general, we also find that these same stabilizing agents'also have the property of imparting greater water resistance to the dried glue.

As jellying agents we have used formaldehyde, paraformaldehyde, trioxymethylene and furfural. Other aldehydes are the equivalents of the above. We also find that carbon bisulphide has the same jellying action, but somewhat longer delayed. We do not wish to limit ourselves as to these specific jellying agents but we claim as equivalents any substances which have the property of producing a jelly when added to a colloidal solution of an oil-seed residue material in the making of an adhesive. We find that special properties of stability may be imparted to the jelly, when the jellying agent is added, stirring being temporarily interrupted.

We find that by treating the finely ground residues of the oil-seeds in the dry state by the action of heat and/or live steam, that we can increase thereby the water requirement of the glue, i. e., we can use more water with the same amount of dry material and thereby increase the amount of wet glue made, and at the same time increase the adhesive strength of the glue. In other words, it is not always true that the thicker the glue. the greater are its adhesive qualities, so far as the vegetable protein glue is concerned. Such treatment also imparts other desirable properties to the resulting jelly. For example, we find that by properly regulating the heat treatment we coagulate a certain amount of the protein material and leave it in such a state that it is not readily dispersed by the usual dispersing action. Such indispersed material acts as a stabilizing agent. By stabilizing agent we mean any compound or material which increases the jelling tendency of a colloidal dispersion, or another way of putting this might be, say, that the stabilizing agent increases the strength of the jell. In general, any agent that increases the water requirement acts as a stabilizing agent. For example, a colloidal dispersion without a stabilizing agent having a dilution of five parts of water to one part of solid, when a jelling agent is added, will just form a jell of a certain consistency and strength. When a stabllizing agent is added; the same colloidal dispersion plus the stabilizing agent may be diluted to 6.5 parts of water to one part of solid, and when the same jelling agent is added as before, it will form a jell of the same strength and consistency asbefore. Or, to put it another way, if the water requirement had been left at five to one, as in the first example, with the stabilizing agent, the strength of the jelly formed would have been much greater. than without the stabilizing agent. When a jelly is subjected to pressure, as between two plies of wood, it is important that the jell structure be strong enough to hold its form until sufilcient drying has taken place to establish adhesion. A weak jelly under pressure may be transformed as a whole to a liquid which is squeezed into the fibres of the wood by the pressure, and adhesion is lost. Stabilizing agents, by increasing the strength of the jell, keep the jell on the glue line and prevent it going over into a liquid as a whole. In the case of a strong jelly, when pressure is applied, water containing onlya small amount of colloidal material leaks out but the balance of the colloidal material re.- tains its jelly form and is not squeezed into the fibres of the wood by the pressure, but remains on the glue-line as a substantial adhesive film.

We have found also that rosin imparts desirable properties in the way of modifying the characteristics of the jelly produced, and we claim as equivalents of rosin in this respect other resins. Rosin imparts to the colloidal jelly which is to be used as a glue, a certain stickiness.- We define a jelly for the purpose of this application as being any form of a colloid and water which when spread between plies of wood and subjected to pressure will not penetrate to any great extent the fibre of the wood, but will retain a major portion of the colloidal material between the plies of wood permitting water containing only a small amount of the colloidal material to escape or to penetrate the wood. From a practical standpoint, these jellies used for glue purposes must be of such a consistency that they can be spread either by a mechanical spreader or by hand. When an adhesive .in a syrupy condition is attempted to be employed on wood which is very wet, no adhesion results, but when the same syrupy adhesive or colloidal compound is treated a good adhesion results. While we do not know the exact explanation, it is thought that the reason is as stated above, namely, that it permits the release of the water with only a small part of the colloidal compound and prevents the dilution of the jelly with the water of the wood.

The processwhich we have discovered for making veneer differs from the two processes set forth in the beginning of this specification in that the wood is not dried down to a low moisture content and heating is omitted, but is put through the spreaders and the glue applied while the wood contains still a considerable percentage of moisture, something above the fibre saturation point, which, in general, may be said to be thirty percent. The process consists in passing damp plies having a moisture point above the fibre saturation point through glue-spreaders, assembling in piles or racks, applying pressure, holding the pressure with clamps for a sufllcient time in order to give the glue a chance to obtain its set, and then either allowing the veneer panel to air-dry or passing the veneer panel through a dryer to more quickly reduce the moisture content downto the final moisture content demanded by the trade into which this particular veneer panel is going, and then dressing said panel, i. e., sand-papering and trimming the same. This final moisture content varies with different veneer panels, and with the purposes for which they are to be used,in general being anywhere from ten to twenty percent.

We have found that the following formula gives, satisfactory results in the production of a vege- It is not necessary to add caustc soda as such,

but caustic soda producing compounds may be substituted.

The method of preparing this formula is as follows:

Two hundred and fifty pounds of water are placed in the mixer at one hundred degrees Fahrenheit, in which is dissolved the permanganate and the lime suspended. To this solution is added one hundred pounds of soya bean flour, stirring the same until the lumps are well removed. Thenanother one hundred pounds of water, cold, are added and four pounds of caustic soda. This is stirred for about ten minutes oruntil dispersion is fairly complete, when is added a third one hundred pounds of water to the mixer, and next the fourth one hundred pounds containing twenty ounces of formaldehyde. About three to five minutes is required for the formaldehyde to completely jell the glue under this condition. It is thought that the addition of the lime increases the water resistances.

With glue made as above, there is some tendency for the glue to diffuse into the wood when pressure is applied. We have found that the addition of one of the weak acids, such as phenol, ,cresol, arsenious or boric acid, with the jellying agent or after addition of the jellying agent. (preferably after), improves the character of the glue with reference to its property of remaining on the glue line.

These weak acids may be used in amounts sulficient to combine with all the alkali present. This,

however, would not produce acidity to phenolphthalein for instance, because the sodium salts of these weak acids are alkaline to phenol-phthalein. These weak acids make only one change in the mechanical behavior of the gel, i. e., they increase the readiness with which the gel will release water. A great difference is noted, however, in the behavior of the gel toward the wood. Additions of such weak acids to the glue cause the glue to remain on the glue line much better than glues to which such additions are not made. Accordingly, such additions result in a considerable practical improvement. We have noted before that it is essential that the jelly between the plies of wood retains its jelly structure and permits water containing only a small amount of colloidal material to escape when the pressure is applied. These weak acids have the property of permitting the jelly to act in this manner, that is, they apparently increase the readiness with which the jell releases water, and at the same time stabilize the major portion of the colloidal material in its jelly form, thereby keeping the colloidal material which is the adhesive from squeezing into the fibre of the wood and being dissipated. Different woods act differently on the same jelly, and we may use these weak acids in varying amounts depending upon the character of the wood. That is, we may use them in amounts only suflicient to neutralize part of the alkali present, or in amounts suificient to neutralize all of the alkali present, or in some small degree of excess over the theoretical amount required to neutralize the alkali. The amounts of acid used must be worked out for the particular wood under consideration. We have found that boric acid is best adapted for addition to the glue, but we do not restrict ourselves to its use inasmuch as other weak acids, such as phenol, cresol, or arsenious acids may be used.

In practice, we have found that the addition of two pounds of boric acid to the formula as given above is quite satisfactory, but we do not desire to restrict ourselvesto this specific amount, as the quantity may be greater or less in accordance with requirements depending upon the nature of the wood to be glued, the tendency or lack of tendency of the glue to diffuse into the wood under pressure applied.

Relative the use of rosin producing a jelly of great stickiness: A second working formula for producing an adhesive which will have. a jellylike consistency such that it will operate under the conditions herein set forth, involving the use of rosin, is as follows: Four hundred pounds of water are placed in the mixer at one hundred degrees Fahrenheit; then three hundred pounds of a glue composed of two hundred twenty five parts soya bean flour and seventy five parts of a mixture of 54.5 parts soya bean flour, 8.2 parts lime, and 12.3 parts of rosin. This mixture of glue and water is stirred until the lumps are well removed,-

then three hundred ten parts of cold water are added, and 12.5 parts of caustic soda dissolved in one hundred twenty five pounds of water. This is stirred for ten minutes and then six hundred eighty five pounds of water are added. Then add the jelly agent, eight and one-third parts of formalin, and sixteen and two-thirds pounds of cresol, all in three hundred fifty pounds of water. After a few minutes final stirring, the glue is ready to use.

This application is a continuation, in common subject matter, of our earlier-application filed March 9th, 1926, Serial No. 93,534.

Other modes of applying the principle of our invention may be employed, change being made as regards the details described, provided the features stated in the following claims, or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:-

1. The method of making a glue in the form of a jelly, which comprises treating a ground oilseed residue in water with a jelling agent and an agent for stabilizing the formed-jell against break-down when heavy pressure is applied, and a weak acid.

2. The method of making a glue in the form of a jelly, which comprises treating a ground oilseed residue in water with ajelling agent and an agent for stabilizing the formed-jell against break-down when heavy pressure is applied, and

rosin.

3. The method of making a glue in the form of a jelly, which comprises treating a ground oilseed residue in water with a jelling agent and an adsorbent agent for stabilizing the formed-jell against break-down when heavy pressure is applied, and a weak acid.

4. The method of making a glue in the form of a jelly, which comprises treating a ground oilseed residue in water with a jelling agent and an adsorbent agent for stabilizing the formed-jell against break-down when heavy pressure is applied, and rosin.

5. The method of making a glue in the form of a jelly, which comprises dispersing a mixture of soya bean flour in the presence of water and rosin, and'then adding an agent for jelling the dispersed material to inhibit undue thinning by wood-moisture before the bond is made.

6. The method of making a glue in the form of a jelly, which comprises dispersing soya bean flour in the presence of water, adding potassium permanganate, an agent for jelling the dispersed material to inhibit undue thinning by woodmoisture before the bond is made, and a weak acid.

7. The method of making a glue in the form of a jelly, which comprises dispersing soya bean flour in the presence of water, adding potassium permanganate, an agent for jelling the dispersed material to inhibit undue thinning by wood-moisture before the bond is made, and boric acid.

8. The method of making a glue in the form of a jelly, which comprises treating soya bean flour with a dispersing agent, an agent for stabilizing the dispersed material against break-down when heavy pressure is applied after being jelled, a jelling agent, and a weak acid.

9. The method of making a glue, which consists of dispersing a mixture of soya bean flour in the presence of water, then adding rosin, an agent for stabilizing the dispersed material against break-down when heavy pressure is applied after being jelled,. and a jelling agent.

10. The method of making a glue in the form of a jelly, which comprises dispersing a mixture of soya bean flour in the presence of water, then adding rosin, an agent for stabilizing the dispersed material against break-down when heavy pressure is applied after being jelled, a jelling agent, and a weak acid.

11. The method of making an adhesive in the form of a jelly, comprising the steps of dissolving about two parts by weight of potassium permanganate and about three eighths part of lime in about two hundred fifty parts of water at a temperature of about one hundred degrees Fah renheit; stirring in the said solution about one hundred parts of soya bean flour, stirring the same until lumps are well removed; adding to the above mixture about one hundred parts of cold water in which about four parts of caustic soda are dissolved, the entire mixture being then stirred for about ten minutes until dispersion is fairly complete; adding a third one hundred parts of water to the above mixture; and adding a fourth one hundred parts of water in which about one and one-fourth parts of formaldehyde is mixed. 7

12. The method of making a glue, which com prises preparing an aqueous alkaline dispersion of an oil-seed flour, and lessening the fluidity of the dispersion and inhibiting its dilution from wood-moisture by incorporation of a formaldehyde compound.

13. The method of making a glue, which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, lessening the fluidity of the dispersion by incorporation of 2. formaldehyde compound, and stabilizing the dispersed material against break-down when heavy pressure is applied by incorporation of an insoluble calcium compound.

14. The method of making a glue, which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, lessening the fluidity of the dispersion by incorporation of a formaldehyde compound, and incorporating as a stabilizing agent calcium carbonate.

15. The method of making a glue, which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, lessening the fluidity of the dispersion by incorporation of 9. formaldehyde compound,.and incorporating as a stabilizing agent calcium phosphate.

16. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content which comprises preparing an aqueous alkaline dispersion of an oilseed flour and lessening the fluidity of the dispersion by the incorporation of an agent for jelling the dispersed material to inhibit undue thinning by such moisture before the bond is made, said agent for jelling being selected from the group consisting of aldehydes and carbon disulphide.

17. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content which comprises preparing an aqueous alkaline dispersion of an oilseed flour, and lessening the fluidity of the dispersion by the incorporation of a jelling agent and an agent for stabilizing the formed jell against breakdown when heavy pressure is applied, said jelling agent being selected from the group consisting of aldehydes and carbon disulphide.

18. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, lessening the fluidity of the dispersion, and incorporating an absorbing agent for stabilizing the dispersed material against breakdown when heavy pressure is applied.

19. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content, which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, lessening the fluidity of the dispersion, and incorporating a colloidal precipitate for stabilizing the dispersed material against break-down when heavy pressure is applied.

20. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content which comprises preparing an aqueous alkaline dispersion of soya bean flour, lessening the fluidity of the dispersion, and incorporating a colloidal precipitate for stabilizing the dispersed material against break-down when heavy pressure is applied.

21. The method of making a glue, suitable for use in uniting plies of material having a relatively high moisture content which comprises preparing an aqueous alkaline dispersion of an oil-seed flour, and safe-guarding such dispersion against excessive dilution from contact with such moisture containing plies by incorporating a substance thickening the dispersion without destroying its spreadability, said thickening substance being selected from the group consisting of aldehydes and carbon disulphide.

22. The method of making a glue, in the form of a jelly, which comprises dispersing soya bean flourin the presence of Water, adding potassium permanganate and an agent for jelling the dispersed material to inhibit undue thinning by wood-moisture before the bond is made, said agent for jelling being selected from the group consisting of aldehydes and carbon disulphide.

23. A glue, comprising a watery dispersion of an oil-seed flour and having its fluidity reduced to a jell by inclusion of a jelling agent and a jell stabilizing agent, whereby on application to wet wood the glue is not dissipated by the water thereof, said jelling agent being selected from the group consisting of aldehydes and carbon disulphide.

' 24. A glue, comprising a watery dispersion of soya bean flour and having its fluidity reduced to a jell by inclusion of a jelling agent and a jellstabilizing agent, whereby on application to wet wood the glue is not dissipated by the water thereof, said jelling agent being selected from the group consisting of aldehydes and carbon disulphide.

GLENN DAVIDSON. CHARLES N. CONE. IRVING F. LAUCKS. HARRY P. BANKS. 

